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Time and Navigation Time and Navigation Presentation Transcript

  • CHAPTER 3 TIME AND NAVIGATION
  • Jet Lag
  • Jet Lag Temporary disruptions of the body’s normal biological rhythms after high-speed air travel through several time zones
  • Time is based on the relationship of Earth and the Sun.
  • Ship’s Clock
  • Ship’s Chronometer in its case Key For Winding Gimbal Ring Gimbal Lock
  • Chronometer A timepiece or timing device with a special mechanism for ensuring and adjusting its accuracy, for use in determining longitude at sea or for any purpose where very exact measurement of time is required
  • Chronometer • Once started, it is never allowed to stop. • A record is kept of whether it is running fast or slow. • Time checks are made against radio time signals.
  • Radio stations in Washington, D.C., and Honolulu, Hawaii, broadcast time signals every 5 minutes, 24 hours a day.
  • Radio station announcement might be: ―When the tone returns, the time will be 8:50 a.m. Eastern Standard Time; 8:50 a.m.‖
  • The ship’s chronometer is then checked against the time signal by the quartermaster. Any error is recorded, and the navigator must take it into consideration when finding position.
  • a.m. Ante Meridiem, p.m. Post or before the Meridiem middle of the day (noon)
  • 24–Hour Clock
  • Why does the military use a 24–hour clock?
  • NAVY AIR FORCE MARINES ARMY All military services use the 24–hour clock.
  • Why does the military use a 24–hour clock? • To avoid the confusion that would result if ―a.m.‖ or ―p.m.‖ were left out of a message • To be consistent with military time in Europe
  • The day begins a fraction of a second after midnight, 0000 and continues past 0100 to noon, 1200. The afternoon continues with 1300 to 2400 (midnight). While 0000 and 2400 are the same time, it is common practice to start each day at 0001 and end it at 2400.
  • As a cadet, you should memorize the 24–hour clock so it becomes second nature when telling time.
  • What time would it be on the 24–hour clock for the following times? A. 7:00 a.m. B. 12:30 p.m. C. 6:50 p.m. D. 9:15 p.m. E. 12:01 a.m.
  • What time would it be on the 24–hour clock for the following times? A. 7:00 a.m. 0700 B. 12:30 p.m. 1230 C. 6:50 p.m. 1850 D. 9:15 p.m. 2115 E. 12:01 a.m. 0001
  • Ship’s Bell Time • Bells are rung every half-hour. • One bell is struck for the first half hour, and one bell is added for each half hour up to eight bells. • After eight bells (four hours), the sequence begins again.
  • Ship’s Bell Time • An odd number of bells marks a half-hour. • An even number of bells marks an hour.
  • Bells are rung only from reveille to taps, but not during divine services or when fog requires that the bell be used as a fog signal.
  • Morning Watch Time Bells Time Bells * 0430 1 0630 5 * 0500 2 0700 6 * 0530 3 0730 7 0600 4 0800 8 * Not normally sounded
  • Forenoon Watch Time Bells Time Bells 0830 1 1030 5 0900 2 1100 6 0930 3 1130 7 1000 4 1200 8
  • Afternoon Watch Time Bells Time Bells 1230 1 1430 5 1300 2 1500 6 1330 3 1530 7 1400 4 1600 8
  • Dog Watch or First Watch Time Bells Time Bells 1630 1 1830 5 1700 2 1900 6 1730 3 1930 7 1800 4 2000 8
  • Dog Watches 1600 — 1800 First dog watch 1800 — 2000 Second dog watch The first and second dog watches straddle the time when the evening meal is traditionally served. Those with the first dog eat the evening meal after being relieved and those with the second dog eat before assuming the watch.
  • Evening Watch Time Bells Time Bells 2030 1 2100 2 2130 3 2200 4 * Bells are not sounded after taps
  • How many bells would be struck at the following times? A. 0600 B. 0930 C. 1600 D. 1830 E. 2000
  • How many bells would be struck at the following times? A. 0600 4 bells B. 0930 3 bells C. 1600 8 bells D. 1830 5 bells E. 2000 8 bells
  • Time is reckoned according to the travel of the Sun once around the Earth each day.
  • In the sixteenth century, the astronomer Copernicus established that the Earth’s Rotation makes the Sun seem to move.
  • The Earth rotates 360° in 24 hours.
  • In 1 hour, the Earth rotates 15°. (360° ÷ 24 hours = 15° per Hour)
  • If the Earth rotates 15° in 1 hour, it will take 4 minutes to rotate 1°: 60 minutes (1 hr) ÷ 15° = 4 minutes Therefore... 1° longitude = 4 minutes of time
  • Time-Arc Relationship Time Arc 24 hours 360° 1 hour 15° 4 minutes 1° 1 minute 15' (minutes) 4 seconds 1' 1 second 15" (seconds)
  • Apparent Motion of the Sun DIRECTION OF TRAVEL Sun Travels at 15° per Hour
  • The Sun is the most convenient reference for reckoning time.
  • Solar Time Time based on the apparent motion of the Sun around the Earth
  • Apparent Time Time based on the apparent position of the Sun from your position. If the Sun is directly over the meridian we are on, we say that it is noon, local apparent time.
  • Sun 23.5° The Earth’s axis is inclined with respect to the plane of its orbit around the Sun.
  • Sun 23.5° Remember, the time required for a complete rotation of the Earth on its axis, relative to the Sun, varies according to the position of the Earth in its orbit.
  • Mean Solar Time It would be confusing if some days had more hours and others fewer because of the Earth’s revolution; therefore mean solar time is used.
  • Mean Solar Time Average solar time, based on the Sun’s apparent journey around the Earth (360°) in exactly 24 hours
  • Local Mean Time (LMT) The time at your location based on the mean position of the Sun — that is 1200, the mean Sun is over your meridian, not the actual Sun
  • The Equation of Time The difference between apparent time and the mean time
  • NAUTICAL ALMANAC 2003 Almanac DEC 31 2002 THRU JAN 1 2004
  • Almanac An annual publication containing a calendar for the coming year, the times of such events and phenomena as anniversaries, sunrises and sunsets, phases of the moon, tides, etc., and other astronomical statistical information and related topics
  • Cesium Atomic Clock Atomic Time or Universal Coordinated Time (UTC)
  • Atomic Time or Universal Coordinated Time (UTC) An internationally agreed-upon time scale based on the frequency of vibrations of the radioactive cesium atom
  • Greenwich Mean Time (GMT) Time based on the relationship of the mean Sun to the prime meridian
  • Zone Time (ZT) Local mean time along each standard time meridian
  • Since one hour is 15°, each time zone is based on a division of the globe into 24 zones of 15° each. A standard time-zone system is fixed by international agreement and by law in each country.
  • Standard Time Zone 15°-wide zone of the Earth that has the same time
  • Zone Description (ZD) The difference in hours between your Zone Time (ZT) and Greenwich Mean Time (GMT) (Use ―+‖ for longitude west, and ―-‖ for longitude east, for example +8)
  • Zone Description (ZD) Letter and a negative or positive number for 1 to 12, east or west of the prime meridian
  • Daylight Savings Time Zone time set ahead 1 hour The practice of advancing standard time by 1 hour in the spring of each year and of setting it back by 1 hour in the fall in order to gain an extra period of daylight during the early evening
  • Daylight savings time is not used in navigation.
  • International Date Line • The 180th meridian • Separates one day from the next
  • Pacific Mountain Central Eastern The continental United States has four standard time zones.
  • Pacific Mountain Central Eastern Eastern Standard Time (EST) is identified as +5 Romeo (R).
  • Pacific Mountain Central Eastern Central Standard Time (CST) is identified as +6 Sierra (S).
  • Pacific Mountain Central Eastern Mountain Standard Time (MST) is identified as +7 Tango (T).
  • Pacific Mountain Central Eastern Pacific Standard Time (PST) is identified as +8 Uniform (U).
  • R 111420Z9 NOV 03 291936Z NOV 03 GMT FM USNS SATURN TO CNO WASH D.C. Most information in navigational tables and naval communications uses GMT, so you must know how to convert the time in any zone to GMT.
  • How Time Zones are numbered • +1 to +12 west of the Prime Meridian • -1 to -12 east of the Prime Meridian
  • The algebraic procedure to go from zone time (ZT) to Greenwich time (GMT), or to go from GMT to ZT, is: GMT = ZT + ZD or ZT = GMT – ZD
  • Example of using ZD to find Greenwich Time (GMT): 1830 (ZT) - 9h 00m (ZD) = 0930 Greenwich Mean Time
  • Example of Computing GMT Your ship is off the coast of Somalia (ZD = –3). The local time is 1600. What is the GMT? GMT = ZT + ZD
  • Example of Computing GMT Your ship is off the coast of Somalia (ZD = –3). The local time is 1600. What is the GMT? GMT = ZT + ZD GMT = 1600 – 3h = 1300
  • Converting GMT greater than 24 Note: If your calculated GMT is greater than 24, subtract 24 from your answer to determine the correct GMT, which will be one day later than your ZT. Example: At 1600 on 4 July in Adak, AL (ZD = +11), GMT is 0300 on 5 July.
  • Change the following zone times (ZT) to Greenwich mean time (GMT): A. 1230 at Pensacola, FL (ZD = +6) B. 1800 at Tokyo, Japan (ZD = –9) C. 2200 at San Diego, CA (ZD = +8)
  • Change the following zone times (ZT) to Greenwich mean time (GMT): A. 1230 at Pensacola, FL (ZD = +6) 12h 30m + 6h = 18h 30m, or 1830 GMT B. 1800 at Tokyo, Japan (ZD = –9) 18h – 9h = 9h, or 0900 GMT C. 2200 at San Diego, CA (ZD = +8) 22h + 8h = 30h , or 0600 GMT on the next day(30h – 24h = 6h)
  • Computing ZT To find ZT, subtract the zone description (ZD) from GMT: GMT – ZD = ZT
  • Norfolk Naval Station Example of Computing ZT You are stationed at Norfolk, VA (ZD = +5). GMT is 1800. What is the local time? GMT – ZD = ZT
  • Norfolk Naval Station Example of Computing ZT You are stationed at Norfolk, VA (ZD = +5). GMT is 1800. What is the local time? GMT – ZD = ZT 18h – 5h = 13h, or 1300
  • Fairbanks, AL Computation of ZD Note: If your calculated zone time is a negative number, subtract your answer from 2400 or 24 hours, to determine your ZT, which will be 1 day earlier than GMT. Example: At 0500 GMT on 28 May, the ZT at Fairbanks, AL (ZD = +10), is 1900 on 27 May.
  • Determine the (ZT) for the following locations at the given GMT: A. Guantanamo, Cuba (ZD = +5; GMT = 1615) B. Singapore (ZD = -8; GMT = 0600) C. Honolulu, HI (ZD = +10; GMT = 0800)
  • Determine the (ZT) for the following locations at the given GMT: A. Guantanamo, Cuba (ZD = +5; GMT = 1615) 16h 15m – 5h = 11h 15m, or 1115 B. Singapore (ZD = -8; GMT = 0600) 6h – (–8h) = 14h, or 1400 C. Honolulu, HI (ZD = +10; GMT = 0800) 8h – 10h = –2h, or 2200 of the previous day (14h – 2h = 22)
  • In writing naval time, it is generally required to place a time zone’s letter after the numbers. Example: 1100 a.m. in Norfolk would be written 1100R
  • San Diego Naval Base If it was 6:30 p.m. in San Diego how would you write it in naval time?
  • San Diego Naval Base If it was 6:30 p.m. in San Diego how would you write it in naval time? 1830U
  • 291936Z JUN 03 DTG Date/Time Group (DTG) • Used in naval communications • Is placed in the message heading • Identifies when a communication was originated
  • Date Time Group (DTG) The date-time group is assigned for identification and file purposes only. The DTG consists of six digits. The first two digits represent the date, the second two digits represent the hour, and the third two digits represent the minutes. Example 221327Z AUG 03 means the 22nd day of August plus the time in Greenwich mean time (GMT).
  • 291936Z JUN 03 DTG Date/Time Group (DTG) A message is originated at 1936Z on 29 June 2003. What is the DTG?
  • 291936Z JUN 03 DTG Date/Time Group (DTG) A message is originated at 1936Z on 29 June 2003. The DTG is 291936Z JUN 03.
  • +5 A ship cruising off the northern coast of Haiti sent a message at 9:00 p.m., August 22, 2003. What is the DTG of the message?
  • +5 A ship cruising off the northern coast of Haiti sent a message at 9:00 p.m., August 22, 2003. What is the DTG of the message? 230200Z AUG 03
  • TIME AND NAVIGATION THE END
  • Q.1. What is the time used in fixing position by celestial navigation?
  • Q.1. What is the time used in fixing position by celestial navigation? A.1. Greenwich mean time
  • Q.2. What is celestial navigation?
  • Q.2. What is celestial navigation? A.2. Finding position by sightings of the Sun, stars, planets, and Moon
  • Q.3. Why is a chronometer used in celestial navigation?
  • Q.3. Why is a chronometer used in celestial navigation? A.3. Because it is a very accurate timepiece
  • Q.4. Why is the ship’s bell time struck every half hour?
  • Q.4. Why is the ship’s bell time struck every half hour? A.4. Bell time originated when a ship’s timepiece was an hour glass which ran out of sand every half hour and had to be turned.
  • Q.5. How do ships at sea ensure their clocks are correct?
  • Q.5. How do ships at sea ensure their clocks are correct? A.5. Time checks broadcast on radio from Washington, D.C., and Honolulu, Hawaii
  • Q.6. Why does the Navy use the 24-hour clock while civilians use the 12-hour clock?
  • Q.6. Why does the Navy use the 24-hour clock while civilians use the 12-hour clock? A.6. 1. Old maritime custom 2. Avoid confusion in message communications 3. Avoid possible confusion because of A.M. and P.M. 4. To be consistent with military time in Europe
  • Q.7. How would you write and say the time 3:30 P.M. and 4:55 A.M. in Navy time?
  • Q.7. How would you write and say the time 3:30 P.M. and 4:55 A.M. in Navy time? A.7. 1530, fifteen thirty hours; 0455, zero four fifty-five hours
  • Q.8. How many bells should be rung at 0730, 1430, and 2000?
  • Q.8. How many bells should be rung at 0730, 1430, and 2000? A.8. 7, 5, 8
  • Q.9. How often and why is the series of bells on a ship repeated?
  • Q.9. How often and why is the series of bells on a ship repeated? A.9. Every 4 hours to coincide with the watch schedule
  • Q.10. When it is noon at our location (longitude), what is the local apparent time at the meridian 180 degrees away from ours?
  • Q.10. When it is noon at our location (longitude), what is the local apparent time at the meridian 180 degrees away from ours? A.10. Midnight
  • Q.11. Why do our calendars have 366 days in a year every four years.
  • Q.11. Why do our calendars have 366 days in a year every four years. A.11. To account for the error in the Earth's revolution in an elliptical (not perfectly circular) path around the Sun
  • Q.12. What is the relationship between time and the arc of the Sun around the Earth?
  • Q.12. What is the relationship between time and the arc of the Sun around the Earth? A.12. The Sun travels an arc of 15 degrees each hour or one degree of arc every four minutes.
  • Q.13. What is solar time?
  • Q.13. What is solar time? A.13. Time measured by using the Sun as a reference point
  • Q.14. What is apparent time?
  • Q.14. What is apparent time? A.14. Time based on the apparent position of the Sun at any given position on the Earth
  • Q.15. What is mean solar time?
  • Q.15. What is mean solar time? A.15. It is the average solar time that is a method to prevent confusion due to the different lengths of days.
  • Q.16. What is local mean time?
  • Q.16. What is local mean time? A.16. The average solar time over a given position for a given time throughout the year - not the true Sun position
  • Q.17. What is Greenwich Mean Time (GMT)?
  • Q.17. What is Greenwich Mean Time (GMT)? A.17. The local mean time at the Royal Observatory in Greenwich, England
  • Q.18. Why is GMT important to remember?
  • Q.18. Why is GMT important to remember? A.18. By international agreement, it is the reference time used for navigation and communications.
  • Q.19. How many time zones are there worldwide?
  • Q.19. How many time zones are there worldwide? A.19. 24
  • Q.20. How many degrees of arc are there in a time zone?
  • Q.20. How many degrees of arc are there in a time zone? A.20. 15 degrees
  • Q.21. What does a date/time group (DTG) include?
  • Q.21. What does a date/time group (DTG) include? A.21. The date, the time, ZD (zone description, usually Z for GMT), month, and last 2 digits of the year Example: 151635Z APR 03
  • Q.22. How many time zones cover the contiguous U.S.?
  • Q.22. How many time zones cover the contiguous U.S.? A.22. Four, EST, CST, MST, PST
  • Q.23. What are zone descriptions for the time zones around the world?
  • Q.23. What are zone descriptions for the time zones around the world? A.23. Zone descriptions are the numbers 1 through 12, prefixed by + west of Greenwich and - east of Greenwich.
  • Q.24. What is the equation for converting zone time to GMT?
  • Q.24. What is the equation for converting zone time to GMT? A.24. GMT = Zone time (ZT) + Zone description (ZD)
  • Q.25. What is Daylight Savings Time?
  • Q.25. What is Daylight Savings Time? A.25. Zone time set ahead one hour (usually in the summer) to extend the time of daylight in the evening. It is NOT used in navigation.
  • Gimbals A contrivance, consisting of a ring or base on an axis, that permits an object, as a ship's compass, mounted in or on it to tilt freely in any direction, in effect suspending the object so that it will remain horizontal even when its support is tipped
  • Chronometer used for celestial navigation.
  • Arc Any unbroken part of the circumference of a circle or other curved line
  • Longitude Measurement of position east or west from the prime meridian
  • To better understand navigation principles, imagine the Earth as standing still at the center of the universe, with the Sun, as well as all the other celestial bodies, moving around the Earth.
  • Rotation (of Earth) Produces the apparent motion of the Sun Revolution (of Earth) Path the Earth takes around the Sun
  • Time Zone Chart of the World
  • Letter Designations Each time zone has a letter designation and zone description.
  • Time Zones Time zones extend 7 ½° from either side of a standard meridian, which are exactly divisible by 15.
  • USS Dwight D. Eisenhower (CVN 69) Remember to use the rule of algebra that two minuses together make a plus. If we were at a position in a time zone east of Greenwich where the zone description was –5, and we wanted to change a GMT of 0600 to our standard zone time, the formula looks like this: GMT 0600 – ZD – (–5) = ZT 1100